Many transportation refrigeration units are powered by internal combustion engines and it is desirable that the starting circuits for such engines by as simple and reliable as possible for remote control operation by the operator of the vehicle having such transportation refrigeration equipment. It is known to provide such internal combustion engine arrangements with a combination electric starting motor and battery charging generator unit for use with direct current source such as the storage battery commonly provided for the refrigeration unit internal combustion engine. When a combination starting motor generator unit is used, the prior art starting circuit arrangements have been complicated by the need to switch the combination motor generator unit from the starting motor circuit mode to a generator circuit mode and it is desirable to simplify the circuits so that only a single ignition switch is required to be operated to start the engine and automatically switch the combination motor generator unit from starter circuit mode to generator circuit mode.